Impact of low iodine density tumor area ratio on the local control of non-small cell lung cancer through stereotactic body radiotherapy

2021 Fiscal Year Final Research Report

• Project/Area Number: 20K16749
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 52040:Radiological sciences-related
• Research Institution: Hirosaki University
• Principal Investigator: Tanaka Mitsuki 弘前大学, 医学部附属病院, 助教 (60814291)
• Project Period (FY): 2020-04-01 – 2022-03-31
• Keywords: Dual Energy CT / ヨード密度腫瘍体積 / 非小細胞肺癌 / 定位照射

Outline of Final Research Achievements

The purpose of this study is to accurately predict the local recurrence rate after radiotherapy from the tumor iodine density obtained by contrast CT using dual-energy CT. In this study, we focused on the tumor iodine density and its area. A comparison of the 3-year local recurrence rates between the group with a low iodine density area ratio of less than 65% and the group with a low iodine density area ratio of 65% or more showed 4.0% and 14.7%, respectively. Low iodine density tumors with a large proportion of tumor area have a high recurrence rate after radiotherapy, which proved to be a useful prognostic index. In tumors with a large proportion of low iodine tumor area, the proportion of hypoxic cells, which is a factor of radiation resistance, is large, and it is considered that the decrease in the efficiency of reoxygenation after irradiation may have an effect.

Free Research Field

Dual Energy CT

Academic Significance and Societal Importance of the Research Achievements

肺癌は、我が国のがん死亡数の第1位である。高齢や合併症により手術不能な症例が近年増加傾向にあり、定位体幹部放射線治療 (SBRT) が代替治療として行われている。SBRT後の局所制御率は90%と良好であるが、10%では局所再発をきたし、更なる治療成績向上が求められる。本研究では治療開始前にdual-energy CTを用いて造影CTを撮像することで、治療開始前に予後予測ができる可能性を見出した。局所再発率が高い症例において放射線治療の総線量・分割回数の変更や、免疫チェックポイント阻害剤・温熱療法・高圧酸素療法の併用等による治療成績の向上の研究に今後繋げるための基礎研究である。